Thermal process for preparing butadiene from butene-2



Feb. 10, 1959 w. c. KEn-H 2,873,301

THERMAL PROCESS FOR PREPARING BUTADIENE FROM BUTENE-2 Filed April 9, 1956 A TTORNEYS 'than can butene-l. jdehydrogenating a nis customary in the yart in converting normal butene THERMAL PROCESS non PRaPnuNGl Willis C. Keith, Lansing, Ill., asisignor'to Sinclair Refining."

Company, New York, Y., a corporation of Maine Application April 9, 1956, Serial No. 577,157 comms. L (ci. 25o-ssc) My invention relates to the `production of butadiene.

It has heretofore been proposed to prepare butadiene by passing normal butenes in admixture with steam in vapor phase and at elevated 1300 lysts.

temperatures of the order of F. into contact with any of a wide variety of cata- The catalysts which have been employed have `isornerizing as well as dehydrogenating activity, and

hence tend to maintain equilibrium between the butene-l and the butene-Z (cis and trans) which are undergoing reaction to form` butadiene.

My experimental work has shown that a butene-2 can be dehydrogenated to form butadiene in much higher yield Therefore, in preparing butadiene by normal butene, it is preferred to employ butene-2 as a starting material and to conduct the `dehydrogenation under conditions leading to a minimumv amount of isomerization of butene-Z to butene-l. Hence,

ythe process which I have invented involves thermally or non-catalytically dehydrogenating butene-Z which is' in a high state of purity,

particularly with respect to butene-l content.

F., the period of temperature generally being from 0.01v second to 0.2 second and preferably from 0.05 second to 0.1 second. As

The dehydrogenation of the butene-2 v- `in accordance with my invention is carried out at an elevated temperature within the range from 1200 F. to l17003 F., preferably 1300 F. to 1500 vtime during which the butene-2 is heated at the elevated normal butenes.

`be recovered from the quenched stream by extractive .of a wide variety of vmethods i which have been described in the Patentd Feb. l0, 1959 of butene2. Steam is the preferred diluent gas. When my` process is carried out, butene-Z is isomerized to butene-l as Well as dehydrogenated to butadiene, and the reaction conditions are adjusted so that the conversion based upon disappearance of normal bu'tenes does not exceed 70 percent. A

. After the butene-Z has been dehydrogenated to pro duce the desired butadiene, the hot gaseous `mixture leaving the converter is quickly cooled, as by quenching, this also being conventional in producing butadiene from The butadiene in puried form can then distillation using acetone or furfural, for example. Other methods can also be employed, such as azeotropic distil- `lation with Aammonia or reaction with cuprous ammonium acetate. vButene-Z present in the quenched stream can be recovered by fractionation and returned to the thermal dehydrogenation step. Butene-l present in the quenched stream can also be recovered by fractionaldistillation and isomerized to butene-2 in very high yield using any which are known and art. Note, for example, Industrial and .Engineering Chemistry 45, 551-565 (1953). Butene-2 formed by the isomerization of butene-l can be used as feed in my process. t

The following example illustrates various embodiments which fall within the scope of my invention.

EXAMPLE Butene-2 (cis and trans) having a purity of 99 percent admixture with steam was passed through a hot tube reactor following which thel effluent from the tube was .quenchedwith water and the reaction products analyzed.

Thereaction conditions are set forth in Table I. The

-reaction temperatures reported in the'. table are average `temperatures taken from th'e temperature proiile of the hot tube, and the contact times are calculated ones based .upon the free space of the hot tube .and the` volume of the gases (steam and butene-2) introduced into the reactor at the average reactor temperature.

Table I Run No 1 2 '3 4 5 5 7 Reaction temp., F 1, 335 1, 405 1, 470 1, 520 1, 590 t, 300 Ca. 1. 270 Contact time, sec...- 0.12 0. ll 0.11 0. 1l 0.10 0. 12 4 0. 12 Mole ratio steam to butene-2.. 20 20 20 20 20 20 20 Conversion (A 25.4 26.0 52. 9 65. 3 91. 0 15. 2 22.1 Conversion (B 49.4 40. 2 56. 6 69.4 est. 92 28. 9 58.0 Product per 100 moles butene-Z decomposed,

m es: l l

40 45 37 39 22 37. 7 18. 4 49 35 6 6 Ca. 1 47. 5 61. 9 Product per 100 moles butene-2 decomposed,

moles to other than buteue-l:

Butadlene 78. 5 69. 2 39. 6 41 22. 0 72 48. 2 Product, Wt. percent of butene-2 feed' Butadiene 19. 2 17. 4 20. 2 25. 9 19. 3 10. 5 10. 3 Butene-L--- 24.0 14.2 3.6 4.1 (C) 35.9 Butene-2 50. 6 69. 8 43. 5 30. 6 9. 0 yB4. 8 42. 0

(A) Based on disappearance of normal butenes. (B) Based on disappearance of butene-2. (C) Split about 71.1 butene-2 and 13.7 butene-l.

butadiene, the butene-2 is decomposed at approximately atmospheric pressure'vand while' it is admixed with a large amount of an inert diluent gas, generally from 5 to 40 moles of diluent gas per mole of butene-Z `and to It wll'be noted that run No. 5 does not conformito my invention inasmuch as in it the conversion based upon disappearance of normal butenes exceeds percent.

Table II sets forth the experimental conditions and results obtained in similarexperiments employing 99 perpreferably from 1 5 `to125 moles of diluent gas pervmole 70 .'.cent purity butene-l as feed lof the normal butenes.

(D) Based on disappearance of normal butenes,

lIt will be noted Lthat .where butenc-l was used as the feed `of butadiene produced per 100 moles of butene feed decomposedA (to materials other than butene-l in the case of butene-2), shows that where the conversion is less than 70 percent the amount of butadiene produced is considerably vlarger where butene-2 is employed as a feed rather than butene-l. Y

Various modilications can be made in the procedures described in Table I to provide other embodiments which :fall within the scope of ,my invention. For example, although in obtaining the data of Table I a feed which was substantially pure butene-Z was used, a butene-Z feed yof somewhat less purity can also be utilized. In general, the. gaseous .mixture pyrolyzed in accordance kwith my invention will be` ka C4 hydrocarbon fraction which` contains at least 80 mole percent of n-butenes, at least 8O mole percent of the normal butenes being butene-Z (cis and trans). impuritiesy in the C., hydrocarbon fraction,- other than normal butenes, will be largelylnormal butaue,

which has a boiling point corresponding closely to those C., hydrocarbon fractions of `sufficient purity with respect to butene-2 content for use in my process can be prepared in accordance with pro- `columnv 115, overhead Table II Run No 1 2 3 4 5 6 7 8 9 10 Reaction temp., F 1, 49 l, 540 1, 425 1, 430 1. 485 1, 345 1, 4915 1, 495 1, 495 A`Contact time, see..--- 0. 13 0 11 0.16 0. 10 0.12 0. 059 0.068 0. 068 0. 06S Mole ratto steam to butene. 20 20 20 20 20 20 20 40 80 Conversion (D) 92. 9 '.9745 78. 3 60. 3 89. 4 22. 8 84. 1 85. l 85. 1

Product per 100 moles butene-1 decomposed, moles: v

Butndlene 17. 0 16 25 27 21 25 24 19. 3 22. 5 Product, Wt. perce Butene-L... 7.1 2.5 19.8 26.1 10.6 73.6 {15.9 14.9 14.9 Buteurs-2--..- 1. 9 3. 6 3. 6 Butadiene 10. 5 16. 1 14. 8 18. 8 16. 7 18. 1 5. 4 19. 6 16. 9 18. l5

drawing a C4 hydrocarbon fractionwhich is essentially a mixture of butenelv and'butene-Z is ffed through lines 1 and 2 into distillation column 3. Butene-l is removed overhead through line 4 and butene-Z is removed as bottoms through lines 5 and 6. The hutene-Z is ladmixed with -steam flowing through line 7 `and the mixture of butene-2 and steam passes'by means. of line 8j into pyrolysis zone 9. Exit gases from the pyrolysis zone pass by means of ,line 10 into quench zone 11, wherein'water introduced through line 12 is employed as a quenching medium. Water is removed through line 13 and hydrocarbon passes by means of line 14 into stabilization from which through line 16 `hydrogen and hydrocarbons having less than 4 carbon atoms are removed. The bottom sfrom stabilization column 15 areA removedA .through line 17 and pass into a butadiene recovery system 18 from which purified butadiene is rcrnoved through line 119. Butene-l recovered `in the butadiene. recovery'systern passesby means `oflines zgand 2J. .intoV butene-l' isomerization unit 22. .Buteue-l everhead from, ,distillation column 3 is also Yintroduced into cedures which` are well known in the art.` Thus, a conxventional butane-butylene stream 4containing isobutane, isobutylene, butyleneal, normal` butane vand. hutyleneeZ can ber separated into :an overhead and a bottoms fraction using a distillation column. The bottorns fraction conf tains normal butane and. butylene-Z and is subjected to extractive distillation with furfural, buty1ene-2, being recovered from the stripper.

MyV process possesses advantage in that Vwhen it is carried out the butene-Z is Chansedto the desired butadiene and also to butene-l, 'a `compound which can be conveniently isomerized to butcue-Z to quantity of feed in my process.

The conversionV of butene-1 to butene-2 can ne .carried ont using various.A

catalysts at moderate temperatures. Among `the vbetter catalysts are alumina (.e. g. Alarco GradeA activated alumina), alumina on clay, bauxite, sulfonic acids, chromium oxide on alumina, nickel70 percent perchloric.a.cid,. orthophosphoric acid, phosphoric acid on diatomaceous.

earth and silica-alumina or silica-alumina-magnesia cracking catalysts. Temperatures of the order of 3002]?. to

this isomerization unit as shown. Butene-2 recoveredin the 'butadiene recovery system is introduced into the pyrolysisrzonje 9 by means of lines Z3, 6 and 8.

I claim: l

l.v A method for the manufacture of butadiene which comprises heating in the 4absence of a catalyst a C, hydrocarbon fraction to a temperature within the range from 12.00 F. to l700 F. While the hydrocarbon fraction'i's inadmixture with from 5 to 40 moles of aninertdiluent gas per mole of butene-Z for a period of time suchjthat the conversion, based upon the disappearance of normal butenes, does not exceed percent, said hydrocarbon fraction containing at least 8O mole percent of normal butenes and at least percent of the normal butenes being butene-2.

\ 2. The method of claim l wherein said inert diluent gas is steam.

3. The method of claim l wherein said hydrocarbon fraction is butene-Z of about 98 percent purity.

4. A method for the manufacture of butadiene which comprises heating in the absence of a catalyst a C4 hydrocarbcm fraction to a temperature within the range frorn- 1300 F. to l500 F. while the hydrocarbon fraction is in admixture with from 15 to 25 moles of an inert Y diluent gasper mole of butene-2 for a period of time `600 Fyand liquid hourly space velocities. (volume. of...

butene-.l per volume of catalyst per hour) of theorderwj` of 2 can be utilized. For example, in order to convert butene-l to butene-2, the butene-l can be passed at, approximately 400 F. into contact with silica gel, activated clay, anhydrous aluminum sulfate or phosphoric Aacid on pumice. Also, if desired, butene?. can be prepared from butene-l by passing the butene-l into contact witheilica alumina-magnesia cracking catalyst or bauxite at 400,

FL The equilibrium between hutene-l and butene-2 with respect to theV percentage ofbutcne-Z is more favorable at lowery temperatures.

The accompanying drawing is a simplifiedflow diagram illustrating how my process cany be carried out.v In the .Such thatthe conversion, based upon the disappearance of normal butenes,l does not exceed 70 percent, said hydrocarbon `fraction containing at least 80 mole percent of normalbutenesand Vat least 80 percent of the normal butenes ,beingy butene-2.

5; The/method of yclaim gas is steam.

6. The method of claim 4 wherein said hydrocarbon fraction isbutene-Z- of about 98 percent purityi jReferences Cited in the. meer this patent UNITED STATES PATENTS Frolich et al.v lune .15, 1943 Reeves -2---- Oct. 30, '1945 4 wherein said inert diluent 

1. A METHOD FOR THE MANUFACTURE OF BUTADIENE WHICH COMPRISES HEATING IN THE ABSENCE OF A CATYLIST A C4 HYDROCARBON FRACTION TO A 1700*F. WHILE THE HYDROCARBON FRACTION IS 1200*F. TO 1700*F. WHILE THE HYDROCARBON FRACTION IS IN ADMIXTURE WITH FROM 5 TO 40 MOLES OF AN INERT DILUENT GAS PER MOLE OF BUTENE-2 FOR PERIOD OF TIME SUCH THAT THE CONVERSATION, BASED UPON THE DISAPPERANCE OF NORMAL BUTENES, DOES NOT EXCEED 70 PERCENT, SAID HYDROCARBON FRACTION CONTAINING AT LEAST 80 MOLES PERCENT OF NORMAL BUTENES AND AT LEAST 80 MOLE PERCENT OF THE MORMAL BUTENES BEING BUTENE-2. 